need a lab report streptococcus mutans need to explain the pathway and lab tests that were done to identify the bacteria strep mutans.

Question

need help writing a lab report for the unknown bacterium streptococcus mutants. I need to explain the pathway and lab tests that were done to identify the bacteria strep mutans. Here are the instructions and results of my experiment below. 

Introduction: Purpose, stated as "In this project". (2) Background information-importance and significance of the experiment and why such experiments are carried out (for students) and why clinically it's important to identify unknown organisms. (2)Brief explanation of an unknown project, in general, including explanations of types of tests (i.e. cultural, biochemical, genetic). (3) Explanation of how our specific unknown project was carried out -written in a clear and concise manner (3)

 

Discussion: Main characteristics and medical background/significance of the organism. (4) Explanation of how the identification was reached (basically walk through your flow chart). The Table and Flow Chart are referred to in the explanation.Include a discussion of DNA sequence results, and if they matched, or if not what happened and how the situation was resolved. (4) Discussion of any errors, flaws, or difficulties with the study; or if no issues what did you like about the project, any suggestions for improvement. (2)

Answer 1

I can provide background that may be helpful from a medical perspective.

Streptotoccus mutans is a facultatively anaerobic, gram positive coccus that is part of normal human oral flora. It is a common contributor to tooth decay. Additionally, it can cause bacteremia (bacterial infection of the blood) and a heart valve infection called endocarditis. This occurs when a dental procedure induces the bacteria into the bloodstream, such as by dislodging plaque or breaking mucosal tissue with instrumentation, causing bacteremia. Once in blood, the bacteria travel through the circulatory system before reaching the heart. They subsequently colonize the heart valve (almost always the mitral valve in the case of S mutans), resulting in infectious endocarditis which is a serious condition with potentially serious complications.

Bacterial species can be identified via cultures. In bacteremia, a positive blood culture is diagnostic. In tissue infectious such as an abscess, a culture of the tissue is needed. Here’s one potential floe by which you might identify S mutans with cultures, gram staining, and biochemical assays. I will be assuming that we know this is a clinically relevant organism which will affect our process of identification (meaning we aren’t considering some bacteria because they don’t cause disease).

1. Gram stain: Gran staining is used to distinguish Gran positive organisms (which stain purple) from gram negative organisms (which stain pink). The differences are due to structural differences between the cell walls of the 2 categories. Gram staining will identify the bacteria as gram positive, narrowing the list of potential species significantly. We can also evaluate the shape of the bacteria via gram stain. S. mutans are cocci in shape which further narrows the list to mainly staph and strep species.
2. Next, we can assess the activity of an enzyme known as catalase to distinguish between staph and strep species. Staphylococcal species are catalase positive, meaning they do have the enzyme. Streptococcal species including S. mutans are catalase negative, meaning they do not express the enzyme. Catalase converts H2O2 to O2 and water and allows the bacteria to protect themselves from the host’s immune system. If we placed H2O2 in a tube with a Catalase positive organism, we would see bubbles from the reaction. In our case, S mutans is catalase negative and will not break down H2O2 so no bubbles will be seen.
3. Hemolysis. At this point, we know we are dealing with some type of Strep species, as we have a gram positive cocci without catalase activity. We can assess for patterns of hemolysis (splitting of red blood cells) to begin distinguishing between strep species. Strep can be alpha hemolytic (partial hemolysis) beta hemolytic (complete hemolysis), or non-hemolytic. S mutans is alpha hemolytic. We will culture our specimen on blood agar and should see partial hemolysis of the surrounding blood which causes a green color to appear on the agar. This indicates we are dealing with an alpha-hemolytic strep species.
4. Optochin sensitivity. Some alpha-hemolytic strep are sensitive to Optochin, others are resistant. Let’s add optochin to the growth media. S mutans are optochin resistant, so they will continue to grow despite the presence of the antibiotic. We’ve now narrowed our list to just a few species.
5. A few tests can help us distinguish between our alpha-hemolytic, optochin-resistant strep species. We could assess for maltose-fermentation, which will be seen when S mutants is grown on a maltose-containing agar. Another species, S. Mitis does not ferment maltose for example. This would be likely sufficient to identify S mutans though other tests can be performed.